1. Field of the Invention
The invention relates to a resin sealing type semiconductor device and a method of manufacturing the same, and a lead frame.
2. Description of the Related Art
A resin sealing type semiconductor device is manufactured by uniting a lead frame and various types of semiconductor dies etc and then resin-sealing these except outer leads and an outer frame. The detail is as follows. First, a lead frame formed by pressing a base metal made of a Cu member etc is provided. The lead frame includes islands to mount semiconductor dies etc on, inner leads having wire-bonding portions etc connected to the bonding pads of the semiconductor dies etc, outer leads extending from the inner leads to the outside of a sealing resin, tie bars supporting the outer leads, an outer frame supporting the whole lead frame, and hanging leads connecting the islands etc and the outer frame in order to support the islands etc divided from the outer frame.
The back surface of the semiconductor die is fixed and die-bonded to the island using a conductive material. The bonding pad on the semiconductor die and the wire-bonding portion on the inner lead are connected by wire-bonding using a gold wire etc. A passive element such as a die capacitor is bridged between the inner leads and also bonded thereto using a conductive material. The lead frame where the semiconductor dies etc are bonded is set in a resin sealing apparatus, resin is injected between the upper mold and lower mold of the resin sealing apparatus in the state where the outer lead portion including the tie bars and the outer frame portion are held therebetween, and the lead frame where the semiconductor dies etc are mounted is resin-sealed. Then, solder plating or the like is applied to the outer leads, and then the tie bars and the outer frame are cut by pressing, and the outer leads are bended according to needs, thereby completing a resin sealing type semiconductor device.
A process of assembling a resin sealing type semiconductor device like this is described in Japanese Patent Application Publication No. 2005-64076 and “Advanced semiconductor packaging technologies by an illustration book” edited by Semiconductor technologies solutions workshop (the first edition issued on Sep. 25, 2007 by Kogyo Chosakai Publishing Co., Ltd.).
In the resin sealing type semiconductor device, usually, the semiconductor die die-bonded to the island on the lead frame is connected to the wire-bonding portion on the inner lead by wire-bonding the pad electrode on the semiconductor die to the wire-bonding portion using an Au wire (a gold wire) as described above. However, since high electric current flows when the output of the semiconductor die is high, the wire for the wire-bonding is needed to be thick. Furthermore, since solder is used for the die-bonding of a power semiconductor die, the wire-bonding at high temperature is difficult. Therefore, in this case, an Al wire (an aluminum wire) that is cheap, low in resistance, and bondable at room temperature is used instead of an expensive Au wire.
When an Au wire is used for the wire-bonding, the portion for the bonding is heated and an alloy of Au and Al is made so as to provide firm bonding by so-called thermocompression bonding. In addition to the heating, ultrasonic waves are often used to increase the bonding force. On the other hand, when an Al wire is used for the wire-bonding, the process is performed at room temperature and thus it is necessary to increase the intensity of ultrasonic waves. This is because it is necessary to break an aluminum oxide film formed on the surface of the pad electrode on the semiconductor die, various oxide films formed on the wire-bonding portion on the lead frame, etc., so as to make the Al wire directly in contact with the aluminum of the pad electrode etc.
In this case, the vibration direction of the ultrasonic waves is in a certain extending direction of the Al wire, and thus it is necessary to concentrate the force on the wire-bonding portion in order to achieve optimum bonding. To this end, one approach is to apply enough force of the vibration of ultrasonic waves to the wire-bonding portion by preventing the force escaping by preventing the wire-bonding portion being isolated on the lead frame.
Furthermore, in the resin sealing type semiconductor device, the passive element etc as well as the semiconductor die may be die-bonded to the island of the lead frame. The die capacitor as the passive element is bridged between the bonding portions on the two different inner leads and bonded thereto.
In this case, when the lead frame is thin, the lead frame is likely to deform by the force applied when the semiconductor die and the passive element are die-bonded or wire-bonded. To address this problem, the hanging leads are provided and connected to the stiff outer frame of the lead frame located on the outside of the package so as to reinforce the mechanical strength.
Since the outer frame of the lead frame connected to these hanging leads is cut and removed at the same time as when the tie bars between the outer leads are cut after the resin sealing, the hanging leads connected to the semiconductor dies etc are also cut and the electrical isolations among the semiconductor dies etc are secured. However, the outer frame may not completely be cut and removed and remain on the side surface of the resin package, and the remaining portion of the outer frame of the lead frame and the hanging lead may remain connected. This may cause shortcircuit between the semiconductor dies etc mounted on the islands etc connected to the hanging leads. A second approach is to eliminate the shortcircuit between the semiconductor dies etc caused by such a remaining portion of the outer frame.